In　this　study,　we　propose　a　new　coupled　hydro-mechanical　model　considering　porous　media　flow　(FDEM-flow)　for　simulating　hydraulic　fracturing,　which　makes　full　use　of　the　unique　topological　connection　between　joint　elements　and　solid　elements　in　the　combined　finite-discrete　element　method　(FDEM).　The　joint　elements　form　the　flow　channel　for　fluid,　through　which　flow　obeys　the　cubic　law.　In　addition,　viscous　forces　of　fluid　are　taken　into　account　in　FDEM-flow.　A　simple　example　with　analytical　solution　is　given　to　verify　the　model.　Then,　the　effects　of　fluid　viscosity　on　hydraulic　fracturing　are　investigated　by　this　model.　The　simulated　results　show　that　when　a　low　viscosity　fluid　is　injected,　the　fluid　infiltrates　the　fracture　rapidly.　The　initiation　pressure　is　lower　than　the　theoretical　value　and　the　breakdown　pressure　is　slightly　larger　than　the　initiation　pressure.　When　high　viscosity　fluid　is　injected,　fluid　infiltrate　into　the　cracks　very　slowly.　The　initiation　pressure　is　close　to　the　theoretical　value　and　the　breakdown　pressure　is　much　larger　than　the　initiation　pressure.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.